/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jms.listener.adapter;

import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.Session;

import org.springframework.jms.support.destination.DestinationResolver;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Return type of any JMS listener method used to indicate the actual response
 * destination alongside the response itself. Typically used when said destination
 * needs to be computed at runtime.
 *
 * <p>The example below sends a response with the content of the {@code result}
 * argument to the {@code queueOut Queue}:
 *
 * <pre class="code">
 * package com.acme.foo;
 *
 * public class MyService {
 *     &#064;JmsListener
 *     public JmsResponse process(String msg) {
 *         // process incoming message
 *         return JmsResponse.forQueue(result, "queueOut");
 *     }
 * }</pre>
 * <p>
 * If the destination does not need to be computed at runtime,
 * {@link org.springframework.messaging.handler.annotation.SendTo @SendTo}
 * is the recommended declarative approach.
 *
 * @param <T> the type of the response
 * @author Stephane Nicoll
 * @see org.springframework.jms.annotation.JmsListener
 * @see org.springframework.messaging.handler.annotation.SendTo
 * @since 4.2
 */
public class JmsResponse<T> {

    private final T response;

    private final Object destination;


    /**
     * Create a new instance
     *
     * @param response    the content of the result
     * @param destination the destination
     */
    protected JmsResponse(T response, Object destination) {
        Assert.notNull(response, "Result must not be null");
        this.response = response;
        this.destination = destination;
    }


    /**
     * Return the content of the response.
     */
    public T getResponse() {
        return this.response;
    }

    /**
     * Resolve the {@link Destination} to use for this instance. The {@link DestinationResolver}
     * and {@link Session} can be used to resolve a destination at runtime.
     *
     * @param destinationResolver the destination resolver to use if necessary
     * @param session             the session to use, if necessary
     * @return the {@link Destination} to use
     * @throws JMSException if the DestinationResolver failed to resolve the destination
     */
    @Nullable
    public Destination resolveDestination(DestinationResolver destinationResolver, Session session)
            throws JMSException {

        if (this.destination instanceof Destination) {
            return (Destination) this.destination;
        }
        if (this.destination instanceof DestinationNameHolder) {
            DestinationNameHolder nameHolder = (DestinationNameHolder) this.destination;
            return destinationResolver.resolveDestinationName(session,
                    nameHolder.destinationName, nameHolder.pubSubDomain);
        }
        return null;
    }

    @Override
    public String toString() {
        return "JmsResponse [" + "response=" + this.response + ", destination=" + this.destination + ']';
    }


    /**
     * Create a {@link JmsResponse} targeting the queue with the specified name.
     */
    public static <T> JmsResponse<T> forQueue(T result, String queueName) {
        Assert.notNull(queueName, "Queue name must not be null");
        return new JmsResponse<>(result, new DestinationNameHolder(queueName, false));
    }

    /**
     * Create a {@link JmsResponse} targeting the topic with the specified name.
     */
    public static <T> JmsResponse<T> forTopic(T result, String topicName) {
        Assert.notNull(topicName, "Topic name must not be null");
        return new JmsResponse<>(result, new DestinationNameHolder(topicName, true));
    }

    /**
     * Create a {@link JmsResponse} targeting the specified {@link Destination}.
     */
    public static <T> JmsResponse<T> forDestination(T result, Destination destination) {
        Assert.notNull(destination, "Destination must not be null");
        return new JmsResponse<>(result, destination);
    }


    /**
     * Internal class combining a destination name
     * and its target destination type (queue or topic).
     */
    private static class DestinationNameHolder {

        private final String destinationName;

        private final boolean pubSubDomain;

        public DestinationNameHolder(String destinationName, boolean pubSubDomain) {
            this.destinationName = destinationName;
            this.pubSubDomain = pubSubDomain;
        }

        @Override
        public String toString() {
            return this.destinationName + "{" + "pubSubDomain=" + this.pubSubDomain + '}';
        }
    }

}
